Arginine-based surfactants alter the rheological and in-plane structural properties of stratum corneum model membranes.

Hypothesis: Amino acid-based surfactants have been proposed as skin permeation enhancers. In this work, we investigated the potentiality of two arginine-based amphiphiles as permeation enhancers by studying their interaction with stratum corneum (SC) model lipid membranes.

Experiments: N-benzoyl arginine decyl- and dodecylamide were tested in comparison with the classical enhancer, oleic acid, and the non-enhancer, stearic acid.

Histidine 19 Residue Is Essential for Cell Internalization of Antifungal Peptide SmAP Derived from the α-Core of the Defensin DefSm2-D in .

The synthetic peptide SmAP (KLCEKPSKTWFGNCGNPRHCG) derived from DefSm2-D defensin α-core is active at micromolar concentrations against the phytopathogenic fungus and has a multistep mechanism of action that includes alteration of the fungal cell wall and membrane permeabilization. Here, we continued the study of this peptide's mode of action and explored the correlation between the biological activity and its primary structure. Transmission electron microscopy was used to study the ultrastructural effects of SmAP in conidial cells.

Interaction of cationic surfactants with DPPC membranes: effect of a novel N-benzoylated arginine-based compound.

Cationic amino acid-based surfactants are known to interact with the lipid bilayer of microorganism resulting in cell death through a disruption of the membrane topology. To elucidate the interaction of a cationic surfactant synthesized in our lab, investigations involving N-benzoyl-arginine decyl amide (Bz-Arg-NHC), and model membranes composed by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were done. Bz-Arg-NHCwas able to penetrate into DPPC monolayers up to a critical pressure of 59.

Peptides Derived From the α-Core and γ-Core Regions of a Putative Flower Defensin Show Antifungal Activity Against .

is the etiological agent of Fusarium head blight (FHB), a disease that produces a significant decrease in wheat crop yield and it is further aggravated by the presence of mycotoxins in the affected grains that may cause health problems to humans and animals. Plant defensins and defensin-like proteins are antimicrobial peptides (AMPs); they are small basic, cysteine-rich peptides (CRPs) ubiquitously expressed in the plant kingdom and mostly involved in host defence. They present a highly variable sequence but a conserved structure.

Asymmetric bilayers mimicking membrane rafts prepared by lipid exchange: Nanoscale characterization using AFM-Force spectroscopy.

Sphingolipids-enriched rafts domains are proposed to occur in plasma membranes and to mediate important cellular functions. Notwithstanding, the asymmetric transbilayer distribution of phospholipids that exists in the membrane confers the two leaflets different potentials to form lateral domains as next to no sphingolipids are present in the inner leaflet. How the physical properties of one leaflet can influence the properties of the other and its importance on signal transduction across the membrane are questions still unresolved.

Bromide counterion as a spectroscopic sensor at the interface of cetyltrimethylammonium micelles.

The strong UV absorption of the bromide in aqueous solution undergoes a remarkable red shift of more than 10 nm induced by the addition of the salts that constitute a saline buffer. The maximum absorption wavelength of the bromide is displaced from approximately 194 nm in ultrapure water to wavelengths above 200 nm, depending on the composition of the solution. The bromide spectrum as counterion of the cetyltrimethylammonium in the surfactant CTAB also shows sensitivity to the aggregation behavior of the tensioactive, being able to detect intermolecular interactions even at concentrations lower than the critical micelle concentration.

Cationic surfactants as antifungal agents.

Fungi-in being responsible for causing diseases in animals and humans as well as environmental contaminations in health and storage facilities-represent a serious concern to health security. Surfactants are a group of chemical compounds used in a broad spectrum of applications. The recently considered potential employment of cationic surfactants as antifungal or fungistatic agents has become a prominent issue in the development of antifungal strategies, especially if such surface-active agents can be synthesized in an eco-friendly manner.

Volume expansion of erythrocytes is not the only mechanism responsible for the protection by arginine-based surfactants against hypotonic hemolysis.

A novel arginine-based cationic surfactant N-benzoyl-arginine dodecylamide (Bz-Arg-NHC) was synthesized in our laboratory. In this paper we study the interaction of Bz-Arg-NHC with sheep and human red blood cells (SRBC and HRBC respectively) due to their different membrane physicochemical/biophysical properties. SRBC demonstrated to be slightly more resistant than HRBC to the hemolytic effect of the surfactant, being the micellar structure responsible for the hemolytic effect in both cases.

Nebulizing novel multifunctional nanovesicles: the impact of macrophage-targeted-pH-sensitive archaeosomes on a pulmonary surfactant.

In this study, a NE-U22 vibrating mesh Omron nebulizer was used to deliver the Lissamine™ rhodamine B 1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine triethylammonium salt (Rh-PE) and 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS)/p-xylene-bis-pyridinium bromide (DPX) double-labelled macrophage-targeted pH-sensitive archaeosomes (ApH, 174 ± 48 nm, -30 ± 13 mV unilamellar nanovesicles made of dioleoyl-sn-glycero-3-phosphoethanolamine: [total polar archaeolipids from the hyperhalophile archaebacteria Halorubrum tebenquichense]: cholesteryl hemisuccinate 4.2 : 2.8 : 3 w : w : w) to J774A.

Interaction of acylated and unacylated forms of E. coli alpha-hemolysin with lipid monolayers: a PM-IRRAS study.

Uropathogenic strains of Escherichia coli produce virulence factors, such as the protein toxin alpha-hemolysin (HlyA), that enable the bacteria to colonize the host and establish an infection. HlyA is synthetized as a protoxin (ProHlyA) that is transformed into the active form in the bacterial cytosol by the covalent linkage of two fatty-acyl moieties to the polypeptide chain before the secretion of HlyA into the extracellular medium. The aim of this work was to investigate the effect of the fatty acylation of HlyA on protein conformation and protein-membrane interactions.

Induction of eryptosis by low concentrations of E. coli alpha-hemolysin.

Uropathogenic strains of Escherichia coli deliver the toxin alpha-hemolysin (HlyA) to optimize the host environment for the spread of infection. It was reported that at high concentrations, the toxin forms pores in eukaryotic membranes, leading to cell lysis, while lower concentrations have appeared to interfere with host-cell-signaling pathways causing cell death by apoptosis. Nevertheless, what is not clear is how often HlyA reaches levels that are high enough to lyse host target cells during the course of an infection.

N-nervonoylsphingomyelin (C24:1) prevents lateral heterogeneity in cholesterol-containing membranes.

This study was conducted to explore how the nature of the acyl chains of sphingomyelin (SM) influence its lateral distribution in the ternary lipid mixture SM/cholesterol/1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), focusing on the importance of the hydrophobic part of the SM molecule for domain formation. Atomic force microscopy (AFM) measurements showed that the presence of a double bond in the 24:1 SM molecule in mixtures with cholesterol (CHO) or in pure bilayers led to a decrease in the molecular packing. Confocal microscopy and AFM showed, at the meso- and nanoscales respectively, that unlike 16:0 and 24:0 SM, 24:1 SM does not induce phase segregation in ternary lipid mixtures with DOPC and CHO.

Boundary region between coexisting lipid phases as initial binding sites for Escherichia coli alpha-hemolysin: a real-time study.

α-Hemolysin (HlyA) is a protein toxin, a member of the pore-forming Repeat in Toxin (RTX) family, secreted by some pathogenic strands of Escherichia coli. The mechanism of action of this toxin seems to involve three stages that ultimately lead to cell lysis: binding, insertion, and oligomerization of the toxin within the membrane. Since the influence of phase segregation on HlyA binding and insertion in lipid membranes is not clearly understood, we explored at the meso- and nanoscale-both in situ and in real-time-the interaction of HlyA with lipid monolayers and bilayers.

Novel evidence for the specific interaction between cholesterol and α-haemolysin of Escherichia coli.

Several toxins that act on animal cells present different, but specific, interactions with cholesterol or sphingomyelin. In the present study we demonstrate that HlyA (α-haemolysin) of Escherichia coli interacts directly with cholesterol. We have recently reported that HlyA became associated with detergent-resistant membranes enriched in cholesterol and sphingomyelin; moreover, toxin oligomerization, and hence haemolytic activity, diminishes in cholesterol-depleted erythrocytes.

Establishing the yeast Kluyveromyces lactis as an expression host for production of the saposin-like domain of the aspartic protease cirsin.

Typical plant aspartic protease zymogens comprise a characteristic and plant-specific insert (PSI). PSI domains can interact with membranes, and a role as a defensive weapon against pathogens has been proposed. However, the potential of PSIs as antimicrobial agents has not been fully investigated and explored yet due to problems in producing sufficient amounts of these domains in bacteria.

Alpha hemolysin induces an increase of erythrocytes calcium: a FLIM 2-photon phasor analysis approach.

α-Hemolysin (HlyA) from Escherichia coli is considered as the prototype of a family of toxins called RTX (repeat in toxin), a group of proteins that share genetic and structural features. HlyA is an important virulence factor in E. coli extraintestinal infections, such as meningitis, septicemia and urinary infections.

Contribution of the C-terminal end of apolipoprotein AI to neutralization of lipopolysaccharide endotoxic effect.

It is well known that high density lipoprotein (HDL) binds bacterial lipopolysaccharide (LPS) and neutralizes its toxicity. The aim of this work was to study changes in the apolipoprotein (apo) AI structure after its interaction with LPS as well as to determine the protein domain involved in that interaction. The presented data indicate that LPS does not lead to major changes in the structure of apoAI, judging from Trp fluorescence spectra.

Relevance of fatty acid covalently bound to Escherichia coli alpha-hemolysin and membrane microdomains in the oligomerization process.

alpha-Hemolysin (HlyA) is an exotoxin secreted by some pathogenic strains of Escherichia coli that causes lysis of several mammalian cells, including erythrocytes of different species. HlyA is synthesized as a protoxin, pro-HlyA, which is activated by acylation at two internal lysines Lys-563 and Lys-689. It has been proposed that pore formation is the mechanism of cytolytic activity for this toxin, as shown in experiments with whole cells, planar lipid membranes, and liposomes, but these experiments have yielded conflicting results about the structure of the pore.

Visualization and analysis of lipopolysaccharide distribution in binary phospholipid bilayers.

Lipopolysaccharide (LPS) is an endotoxin released from the outer membrane of Gram-negative bacteria during infections. It have been reported that LPS may play a role in the outer membrane of bacteria similar to that of cholesterol in eukaryotic plasma membranes. In this article we compare the effect of introducing LPS or cholesterol in liposomes made of dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine on the solubilization process by Triton X-100.

Fatty acids covalently bound to alpha-hemolysin of Escherichia coli are involved in the molten globule conformation: implication of disordered regions in binding promiscuity.

Alpha-hemolysin (HlyA) is a pore-forming toxin secreted by pathogenic strains of Escherichia coli. The toxin is synthesized as a protoxin, ProHlyA, which is matured in the cytosol to the active form by acylation at two internal lysines, K563 and K689 (HlyA). It is widely known that the presence of fatty acids is crucial for the hemolytic and cytotoxic effects of the toxin.

Paradoxical lipid dependence of pores formed by the Escherichia coli alpha-hemolysin in planar phospholipid bilayer membranes.

alpha-Hemolysin (HlyA) is an extracellular protein toxin (117 kDa) secreted by Escherichia coli that targets the plasma membranes of eukaryotic cells. We studied the interaction of this toxin with membranes using planar phospholipid bilayers. For all lipid mixtures tested, addition of nanomolar concentrations of toxin resulted in an increase of membrane conductance and a decrease in membrane stability.

[Advances in the development of neutralizing therapies for sepsis].

Lipopolisaccharide (LPS), also called endotoxin, is the major component of the external membrane in Gram negative bacteria. This molecule is released to circulation by the bacteria, producing a large variety of toxic and pro-inflammatory effects which are associated with lipid A as well as with sepsis pathogenesis. Many physiological phenomena produced by LPS arise from this molecule's capacity to activate cells in the host immune system such as monocytes, macrophages and polymorphonuclear leukocytes.

[Therapeutic applications of pore-forming lytic toxins: potential use of Escherichia coli alpha-hemolysin].

Many infectious bacteria export soluble proteins which can damage the plasma membrane of eukaryotic cells. Most often they are directed against leukocytes for the purpose of reducing the immune response of the host. In some cases, these toxins are also hemolytic.